1. Field of the Invention
The present general inventive concept relates to a brushless DC motor, and more particularly, to a brushless DC motor to reduce torque ripple, thereby reducing vibration and noise and enhancing an operating efficiency.
2. Description of the Related Art
Generally, motors are used in various electronic products to generate a rotational driving force. The motors include a brushless DC motor which can be reduced in volume and weight and can be easily controlled in its speed.
A conventional brushless DC motor disclosed in Japanese Patent Laid-open Publication No. 2002-84693 comprises a stator, a rotor rotatably received within the stator, and a rotational shaft passing through a center of the rotor. The stator comprises a stator core formed by a plurality of magnetic steel plates stacked in a substantially cylindrical shape, a plurality of slots circumferentially arranged at the stator core, and a plurality of coils wound around the plurality of slots.
The rotor comprises a rotor core formed with a plurality of magnetic steel plates stacked in a substantially cylindrical shape and fitted into a hollow portion formed at a center of the stator in a state of being spaced a predetermined distance from each other, a plurality of installing holes arranged in a circumferential direction within the rotor core, and a plurality of magnets respectively fitted into the plurality of installing holes, in which the rotational shaft is press-fitted into the hollow portion to rotate with the rotor.
Accordingly, when current is applied to the plurality of coils wound around the plurality of slots of the stator, the respective coils are subjected to sequential variation in polarity, so that centrifugal force is generated by virtue of a repulsive force generated when the polarity of the respective magnets of the rotor is the same as that of the respective coils of the stator and an attractive force generated when the polarity of the respective magnets of the rotor is different from that of the respective coils of the stator, whereby the rotor rotates along with the rotational shaft, and generates the rotational driving force.
However, since the conventional brushless DC motor constructed as described above is not equipped with a structure for preventing a magnetic flux from being disconnected or leaking between the respective installing holes into which the magnets are fitted, it structurally suffers a great amount of torque ripple, thereby increasing noise and vibration and deteriorating an operating efficiency.